The present invention relates to an electronic speed governor for an air-compression internal-combustion engine, and more specifically, to an electronic speed governor that has means for sensing operating values of the engine and means for measuring an absolute pressure to determine air mass for the engine.
Electronic diesel control (see Automobil-Industrie (Automobile Industry) 5/86 "Elektronische Dieselregelung" (Electronic Diesel Control"), page 653 ff.) ensures an accurate presetting of the fuel-injection quantity for any driving performance required by the driver. The electronic diesel control allows for environmental criteria and the criteria for permissible operating ranges of the internal-combustion engine. In the described control system, system sensors provide to an electronic control unit signals relating to the control-rod travel, the injection-pump speed, the position of the accelerator pedal, the charge-air and fuel temperature and the supercharging pressure. A correcting variable formed from these signals serves as a measure for determining values for the permissible injection masses, these values then being stored in a data module.
Depending on the speed of the internal-combustion engine and the correcting variable, either the exhaust-gas temperature or the blackening value (smoke) or the peak pressure is a limiting variable. Limiting areas, such as the smoke-limit, are identified in the family of full-load quantity characteristics (FIG. 13 of the above-mentioned publication). By close adherence to the predetermined smoke-limit curves, smoke emissions are reduced compared to those of conventional internal combustion engines that do not have smoke-limiting measures. However, because the smoke-limit is restricted to permissible values, desirable driving performance is not obtained at high altitude.
An objective of the present invention is to provide an electronic speed governor that allows the power capacity of the internal-combustion engine to be utilized as effectively as possible, even at high altitudes.
This and other objects are met by the present invention which provides an electronic speed governor for an aircompression internal-combustion engine that has means for sensing operating values of the internal-combustion engine and means for measuring an absolute pressure to determine air mass for the internal-combustion engine. A control unit has stored smokelimit curves, and is coupled to the means for sensing and the means for measuring. The control unit receives as inputs the operating values and the determined air mass and controls the fuel mass as a function of the operating values, the air mass and the stored smoke-limit curves. The control unit shifts the smoke-limit curves such that the smoke emission of the internalcombustion engine remains constant in response to decreasing atmospheric pressure. The control unit will correct a fuel mass according to the shifted smoke-limit curve.
Because the smoke-limit curve is raised as a function of the altitude at which the engine is operating, without entering the range of impermissible smoke emission, the best possible utilization of the power capacity of the internal-combustion engine can be obtained for a particular operating state. Thus, the blackening value that would be otherwise reduced in the conventional manner at high altitude by the electronic system is maintained at permissible values.
The lowered blackening value or the visible blackening at high altitude in relation to the same excess air for combustion arises because, in measurement terms, the same exhaust-gas volume is detected for determining the visibility of the blackening and is evaluated in respect of the particles. In relation to the evaluated volume, therefore, the tested exhaust-gas mass or its particle content is smaller than at sea level, because the air density becomes lower with increasing altitude. In the electronic control, the fuel mass and the air mass are interrelated for the same smoke.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.